Disclosure of Invention
The invention aims to provide a charger with a small volume and a high space utilization rate and a high power density structure.
In order to solve the technical problems, the invention adopts the technical scheme that:
the charger with the high power density structure comprises a shell, a control circuit board and a transformer, wherein the control circuit board and the transformer are arranged in the shell, and the charger is characterized in that: the control circuit board is divided into a main circuit board and an auxiliary circuit board, the transformer is installed on the main circuit board, and the auxiliary circuit board is arranged above the main circuit board and close to the top end face of the transformer in an up-and-down overlapping mode through a vertically arranged supporting seat; and a power control chip U1 made of ultra-high integration gallium nitride is connected between the primary side and the secondary side of the transformer in a bridging manner.
The transformer is installed on the upper surface of main circuit board through the stabilizer blade that sets up in magnetic core skeleton bottom, power control chip U1 is installed on the lower surface of main circuit board, the height of stabilizer blade is at 1.5mm-3.0 mm.
The PWM circuit, the synchronous rectification circuit, the EMI suppression circuit and the filter circuit of the charger are arranged on the main circuit board; the input/output connection port and the protocol decoding circuit of the charger are arranged on the secondary circuit board.
The model of the power supply control chip U1 is INN 3379C; the PIN24 of the power control chip U1 is connected to a PIN4 on the primary side of the transformer, PIN16-PIN19 of the power control chip U1 are connected in parallel to the grounding end of the primary side of the transformer, PIN14 of the power control chip U1 is connected to PIN3 on the primary side of the transformer through a third MOS tube Q3, PIN1 and PIN2 ends of the power control chip U1 are overcurrent protection ends, PIN9 of the power control chip U1 is connected to the grid of the first MOS tube Q1, PIN11 of the power control chip U1 is connected to the common end of the drain of the first MOS tube Q1 and the secondary side B point of the transformer through a resistor R10, and PIN10 of the power control chip U1 is connected to the common end of the positive electrode of an output capacitor C6 and the positive electrode of the capacitor C7 and the secondary A point of the transformer.
The supporting seat is made of plastic materials, and the supporting seat is arranged on the side of the main circuit board and consists of a transverse seat and a longitudinal seat, the transverse seat is arranged at one end of the side of the main circuit board, the longitudinal seat is arranged at the other end of the side of the main circuit board, a plurality of upwards extending supporting columns are respectively arranged on the transverse seat and the longitudinal seat, the supporting plate is fixedly sleeved on the upper part of each supporting column, the auxiliary circuit board is supported on the supporting plate of the transverse seat and the longitudinal seat and fixedly connected with the supporting plate, and the USB interface of the charger is arranged in a neutral position formed by enclosing the upper surfaces of the auxiliary circuit board, the transverse seat, the longitudinal seat and the main circuit.
The bottom surface and the top surface of the magnetic core and the framework are respectively provided with a notch, the notch on the top surface is used for placing a secondary flying wire of the transformer, and the notch on the bottom surface is just tangent to the protruded part of the framework.
Pouring sealant with a heat conduction function is poured between the main circuit board where the support legs are located and the bottom surface of the transformer.
The length and the width of the main circuit board are (32mm-36mm) × (32mm-36mm), and the power density is 17W/in3-19W/in3。
The invention adopts a novel power control chip made of ultra-high integration gallium nitride to be bridged between the primary and secondary sides of the transformer, so that the power control chip integrates a control part and also integrates a power switch device and signal feedback, thereby effectively saving space and improving the power density of the charger. By improving the circuit structure, the circuit control system of the charger is respectively arranged on the two circuit boards (namely the main circuit board and the auxiliary circuit board), then the two circuit boards are arranged in a manner of being overlapped at intervals from top to bottom, and the space between the two circuit boards is used for arranging a Type-C interface, so that the space utilization rate is further improved. The power density of the charger of the invention can reach 17W/in3Namely, under the condition of the same overall dimension of the charger, the output power of the charger can be more than 3 times of that of the charger in the prior art.
Detailed Description
Firstly, a novel power supply control chip U1 with ultrahigh integration level is adopted.
1. The charger with the high-power-density structure adopts a power supply control chip U1 with ultrahigh integration level, the model number is INN3379C, the chip is bridged between the primary and secondary sides of a transformer 1 (the symbol in the circuit of figure 8 is T1, the same below), a pulse width modulation circuit, a synchronous rectification control circuit, a magnetic coupling feedback circuit and gallium nitride replace the traditional MOS to be used as a switching device and the like are integrated, and due to the ultrahigh integration of the power supply control chip, the circuit arranged at the periphery of the chip is very concise and saves space, the conduction internal resistance of the gallium nitride is very small, the conversion efficiency of the charger is improved, and the heat productivity of the charger is reduced.
The GaN advantage of the gallium nitride as a third-generation semiconductor material is remarkable. Because the forbidden band width is large and the heat conductivity is high, the GaN device can work at the high temperature of more than 200 ℃, can bear higher energy density and has higher reliability; the large forbidden band width and the insulation breakdown electric field of the device reduce the on-resistance of the device, and are beneficial to improving the integral energy efficiency of the device; and the electron saturation speed is high, and the carrier mobility is high, so that the device can work at high speed.
2. As shown in fig. 8, 8a and 8b, the circuit connection relationship between the power control chip U1 and the primary and secondary sides of the transformer 1 is as follows:
the PIN24 of the power control chip U1 is connected with the PIN4 of the primary side of the transformer 1, and gallium nitride materials are integrated inside the power control chip U1 to replace the traditional MOS. PIN16-PIN19 of the power control chip U1 are connected in parallel with the grounding end of the primary side of the transformer 1, are used for heat dissipation of the power control chip U1, and simultaneously form a power loop of the primary side of the transformer 1 together with PIN24 of the power control chip U1.
PIN2 and PIN3 of the transformer 1 are power supply windings of the chips, and power is supplied to the primary side of the power control chip U1 through PIN14 of the power control chip U1 after rectification of a diode D6, filtering of a capacitor C4, voltage stabilization of a third MOS tube Q3, current limiting of a resistor R4 and filtering of a capacitor C15.
The PIN14 of the power control chip U1 is connected to the PIN3 on the primary side of the transformer 1 through a third MOS transistor.
The PIN1 and PIN2 ends of the power control chip U1 are overcurrent protection ends, and are connected to one end of a resistor R9, when output current passes through the resistor R9, voltage difference can be generated at two ends of the resistor R9, and when the PIN2 PIN voltage of the power control chip U1 exceeds a threshold value, output is closed, so that overcurrent protection is achieved.
And a PIN4 of the power control chip U1 is connected with a capacitor C16 to filter the secondary power supply of the transformer 1.
The PIN9 of the power control chip U1 is connected with the gate of the first MOS transistor Q1 to provide a driving signal for the synchronous rectification first MOS transistor Q1.
The PIN11 of the power control chip U1 is connected to the common connection end of the drain of the first MOS transistor Q1 and the point B on the secondary side of the transformer 1 through a resistor R10 and is used for rectification detection.
The PIN10 of the power control chip U1 is connected to the common connection end of the anode of the output capacitor filter capacitor C6, the anode of the capacitor C7 and the point A on the secondary side of the transformer 1, and is used for detecting the output voltage and inputting the power supply of the chip.
The PIN8 of the power control chip U1 is connected to the gate of the second MOS transistor Q2 and is used for output voltage turn-off control.
The PIN5 and PIN6 of the power control chip U1 are connected to the PIN2 and PIN3 of the protocol chip U2, respectively, for data and clock signal transmission.
The PIN7 of the power control chip U1 may provide power to the protocol chip U2.
And secondly, arranging a circuit board.
As shown in fig. 1 and 2, the control circuit board disposed in the charger housing is divided into a main circuit board 2 and an auxiliary circuit board 3, the main circuit board 2 is a large board, and the auxiliary circuit board 3 is a small board.
A transformer 1 of the charger is installed on a main circuit board 2, and a PWM circuit, a synchronous rectification circuit, an EMI suppression circuit and a filter circuit of the charger are arranged on the main circuit board 2.
The input/output connection port (for example, Type-C interface 5 providing connection port for charging device) and the protocol decoding circuit (mainly including protocol chip U2) of the charger are provided on the secondary circuit board 3, which is advantageous in that: the simple structure and the protocol decoding circuit are arranged on the auxiliary circuit board 3.
When the PIN5 PIN6 PIN8 PIN9 of the protocol chip U2 receives the requirements of voltage, current and the like sent by the charging equipment, the requirements are decoded first and then transmitted to the power supply control chip U1 through the PIN2 and the PIN3 of the protocol chip U2, so that the output specification of the charger is adjusted.
The main circuit board 2 and the sub circuit board 3 are mounted on one side of the transformer 1 in a vertically spaced-apart stacked arrangement. The auxiliary circuit board 3 is fixedly connected to the position, close to the top end face of the transformer 1, above the main circuit board 2 through a vertically arranged supporting seat 4.
The supporting seat 4 is made of plastic materials, and is arranged on the side of the main circuit board 2 and composed of a transverse seat 41 and a longitudinal seat 42, the transverse seat 41 is arranged at one end of the side of the main circuit board 2, the longitudinal seat 42 is arranged at the other end of the side of the main circuit board 2, a plurality of support columns 43 extending upwards are respectively arranged on the transverse seat 41 and the longitudinal seat 42, the support plate is fixedly sleeved on the upper part of each support column 43, the auxiliary circuit board 3 is supported on the support plates of the transverse seat 41 and the longitudinal seat 42 and fixedly connected with the support plates (the auxiliary circuit board 3 and the support columns 43 can be made into a quick connection structure of male and female plug terminals), and the USB interface of the charger is arranged in a neutral position formed by enclosing the upper surfaces of the auxiliary circuit board 3, the transverse seat 41, the longitudinal seat 42 and the.
By adopting the arrangement of the main circuit board 2 and the auxiliary circuit board 3, the space utilization rate in the shell can be maximized, the area of the PCB is reduced on the horizontal plane, and particularly, the assembly efficiency of the auxiliary circuit board 3 can be greatly improved by utilizing the assembly mode of male and female plug-in terminal connection.
The main circuit board 2 is rectangular, the length multiplied by the width is (32mm-36mm) × (32mm-36mm), and the power density is 17W/in3-19W/in3。
And thirdly, improving the transformer 1.
1. The magnetic core 7 and the framework 6 adopted by the transformer 1 of the charger are customized and opened, and the transformer 1 is an indispensable device in a switching power supply, and the size of the transformer 1 determines the output power of the transformer 1 and the external dimension of the charger, so that the magnetic core 7 and the framework 6 with more ideal shapes and sizes are developed in a mode of customizing and opening the mold, so that higher output power can be obtained, the external dimension of the charger can be reduced, and the aim of improving the power density of the charger is finally achieved.
2. The transformer 1 is arranged on the upper surface of the main circuit board 2 through the support legs arranged at the bottoms of the magnetic core 7 and the framework 6, the power supply control chip U1 is arranged on the lower surface of the main circuit board 2, the magnetic core 7 adopts a horizontal mounting structure, the distance from the magnetic core 7 to the power supply control chip U1 can be effectively increased, heat accumulation is avoided, meanwhile, the height of the support legs is arranged to be 1.5mm-3.0mm, the vertical distance between the power supply control chip U1 and the transformer 1 is further increased, meanwhile, pouring sealant is poured between the main circuit board 2 where the support legs are located and the bottom surface of the transformer 1, and the heat conduction effect is achieved again. The advantages of the structure are: the heat dissipation of the power control chip U1 is facilitated.
As in the prior art, the pouring sealant is poured into the vacant space in the casing of the charger, so that on one hand, heat in the casing is led out quickly through the casing, and on the other hand, the anti-falling capability of the charger can be improved.
Glue pouring and heat dissipation: the conversion efficiency of the charger in the prior art is low, the radiating fins are required to be used for radiating, and the temperature rise of the shell is very high due to glue filling. In the invention, because gallium nitride is used as a switching element, the conversion efficiency of the charger is improved (the conversion efficiency of the charger can be improved by more than 3 percent), the heat productivity is reduced, the pouring sealant can be safely used only by reducing a small part of heat, the pouring sealant flows in from the gap of the product, after the pouring sealant flows in, the pouring sealant is melted with all electronic components on the circuit board into a whole, and the pouring sealant plays an auxiliary heat dissipation function for the electronic components which generate heat, thereby reducing the phenomenon of heat energy consumption power output and improving the power output.
3. The bottom surfaces and the top surfaces of the magnetic core 7 and the framework 6 are respectively provided with the notches 8 so as to lead out secondary flying leads of the transformer 1 conveniently, the situation that a coil is higher than the edge of the magnetic core 7 is avoided, the notches 8 on the bottom surfaces are just tangent to the protruding part of the framework 6, the height size of the transformer 1 can be effectively reduced, and the overall height of the transformer 1 can be effectively controlled through the improvement (shown in figures 3, 4 and 5).
4. Since the larger the area of the center leg 61 of the magnetic core 7, the larger the power that can be output, the elliptical design of the center leg 61 of the magnetic core 7 increases the cross-sectional area of the center leg 61 of the magnetic core 7 and controls the height of the magnetic core 7.
5. In the switch power supply, the primary and the secondary of the transformer 1 must be isolated to ensure the safety of a user, and the common isolation mode is to increase the distance from the primary to the secondary or to isolate by a plastic part, the invention adopts the integrated plastic partition plate 9 to isolate the primary from the secondary, on one hand, the side plate of the integrated plastic partition plate 9 also plays a further supporting role for the secondary circuit board 3 to ensure that the Type-C interface 5 arranged between the main circuit board 2 and the secondary circuit board 3 cannot be inclined because of the inclination of the secondary circuit board 3, namely, the Type-C interface 5 is accurately positioned (see figures 1, 6 and 7).
6. The invention adopts through hole reflow soldering to ensure the reliability and the conductivity of the soldering of each component on the double-sided circuit board.
Common component soldering processes include wave soldering and reflow soldering, and when the two processes are combined together, the reflow-soldered components need to be blocked in a jig mode to avoid the dropping of the components caused by secondary tin application, and since the blocking needs to have space. The circuit board in the charger adopts the double-sided board, when the sufficient welding space is not available, the solder paste is printed on the bonding pad position on the upper surface of the double-sided board, at the moment, the pin hole of the plug-in component is a through hole, the solder paste printed on the upper surface flows to the lower surface through the pin hole of the component for welding, and the component which originally needs wave soldering is soldered with tin in a reflow soldering mode, so that the size of the PCB is reduced, and the power density is improved.
The method can minimize the bonding pad of the element, and the space utilization rate of the plug-in element in the shell is fully improved through the PCB via hole welding.